The Direct Assignment Option as a Modular Design Component: An Example for the Setting of Two Predefined Subgroups

Table 3

Simulation study results based on 500 simulated trials. Sample size and treatment effects as specified in Table 2. Statistical properties of the 2-subgroup direct assignment option design with 1 IA (DAD-1) versus a 2-subgroup balanced randomized design with 1 interim analysis (BRD-1). One-sided and for the subgroup main effects; two-sided for the post-hoc test for an interaction effect.

(a)

Separate subgroup main effects
Case	M+ subgroup				M− subgroup
	Power		Type I error rate		Power		Type I error rate
	DAD-1	BRD-1	DAD-1	BRD-1	DAD-1	BRD-1	DAD-1	BRD-1
I (no interaction)	78.4	78.8	23.8	20.6	79.8	81.8	20.8	18.6
II (interaction)	78.4	78.8	23.8	20.6	82.8	84.4	19.0	18.2

(b)

Subgroup-treatment interaction effect
Case	Power		Type I error rate
	DAD-1	BRD-1	DAD-1	BRD-1
I (no interaction)	—	—	11.3	11.4
II (interaction)	64.3	67.6	—	—